Methods and apparatuses for processing sheets of securities, especially banknotes, into bundles of securities and stacks of bundles of securities (so-called “finishing” methods and apparatuses) are already known in the art.
Such finishing methods and apparatuses are for instance disclosed in U.S. Pat. No. 3,939,621, U.S. Pat. No. 4,045,944, U.S. Pat. No. 4,283,902, U.S. Pat. No. 4,453,707, U.S. Pat. No. 4,463,677, U.S. Pat. No. 4,558,557, U.S. Pat. No. 4,558,615, U.S. Pat. No. 4,653,399, European patent application No. EP 0 656 309, International application No. WO 01/49464, European patent application No. EP 1 607 355, and International application No. WO 2008/010125, all in the name of the present Applicant. A particularly advantageous solution is disclosed in International application No. WO 2004/016433 also in the name of the present Applicant, which solution is incorporated herein by reference in its entirety and is particularly suitable for the production of an uninterrupted flow of securities with a consecutive numbering sequence. Other known solutions are disclosed in European patent application No. EP 0 598 679, International application No. WO 2005/018945, International application No. WO 2006/131839 and British patent application No. GB 2 262 729.
As explained in the above-identified publications, it is common practice in the art to produce securities in the form of sheets or successive portions of a continuous web each carrying a plurality of security prints arranged in a matrix of rows and columns, which sheets or successive portions of web are ultimately cut to form individual securities, usually after numbering of each security prints.
The term “sheet” will be understood in the following as referring equally to an individual sheet as used in sheet-fed printing presses or to a portion of a continuous web as used in web-fed printing presses, which portion of continuous web is ultimately cut into a sheet after the last web printing operation. At the start of the finishing process, a predetermined number of consecutive sheets (typically hundred sheets) are commonly stacked one above the other to form consecutive stacks of sheets, which sheet stacks are then processed one after the other so as to be cut row-wise and column-wise between the security prints to produce individual bundles of securities. These bundles are then usually stacked to form bundle stacks, typically of ten bundles each.
FIG. 1 schematically illustrates a top view of a sheet stack processing system, generally designated by reference numeral 1, for processing stacks of sheets into individual bundles, which system operates in a manner similar to what is disclosed in U.S. Pat. No. 4,283,902 (see also U.S. Pat. Nos. 4,453,707, 4,463,677, 4,558,557, 4,558,615, and 4,653,399). This processing system is adapted to process sheets at a typical rate of 10,000 sheets per hour. Reference SS designates in this example a given stack of sheets, typically comprising hundred consecutive sheets stacked one upon the other. As already mentioned, it shall be understood that each sheet carries an array or matrix of security prints printed thereon, which array will be defined as consisting of M columns and N rows. The actual number of columns and rows of security prints on the sheets obviously depends on the sheet dimensions and on the dimensions of each security print.
Within the scope of the present invention, and for the sake of clarity, the term “column” should be understood as referring to the arrangement of security prints one next to the other along a first dimension of the sheets, hereinafter referred to as the “sheet length”, while the term “row” should be understood as referring to the arrangement of security prints one next to the other along the other dimension of the sheets, hereinafter referred to as the “sheet width”, as schematically illustrated in FIG. 2. Strictly speaking, the terms “column”/“row” and “sheet width”/“sheet length” are however interchangeable. According to the above definition, the sheet length typically corresponds to the dimension of the sheets (or web portions) parallel to a transport direction of the sheets (or of the continuous web) through the printing press or presses that were used to carry out the printing operations, while the sheet width corresponds to the dimension of the sheets transversely to the transport direction of the sheets (or of the continuous web). The sheet width is typically greater than the sheet length.
As is typical in the art, the dimensions (whether of individual sheets processed on sheet-fed printing presses or of successive web portions of a continuous web processed on web-fed printing presses) may for instance be as much as 820 mm in width per 700 mm in length (i.e. 820×700 mm). With such sheet dimensions, six (M=6) columns per ten (N=10) rows of security prints with dimensions of e.g. 130×65 mm might for instance be provided on the sheets. With sheet dimensions of 740×680 mm, four (M=4) columns per seven (N=7) rows of security prints with dimensions of e.g. 180×90 mm might for instance be provided on the sheets. For small sheet dimensions, e.g. of 420×400 mm, four (M=4) columns per six (N=6) rows of security prints with dimensions of e.g. 100×60 mm might for instance be provided on the sheets. The above examples are of course given for the purpose of illustration only.
In the schematic illustration of FIG. 1, each sheet carries five (M=5) columns per ten (N=10) rows of security prints, i.e. fifty security prints per sheet. The sheet stack SS is first fed stepwise (along direction y in FIG. 1) through a first cutting station CS1 where the stack SS is cut along the rows of security prints so as to output successive sets of bundle strips S of securities. In this example, ten (N=10) such bundle strips S of securities are produced as a result of the row-wise cutting of each stack SS, each bundle strip S of securities encompassing a given number of security prints, namely five hundred (i.e. M=5 times hundred) security prints in this case (i.e. the equivalent of five bundles of hundred securities each). In the process, margins (not illustrated) at the front and trailing edges of the sheets are typically cut and discarded as well.
Each bundle strip S of securities is then typically fed in sequence through a banding station BS comprising multiple banding units distributed along the length of each bundle strip S of securities (i.e. along direction x in FIG. 1) to provide a securing band around a corresponding one of the plural positions on the bundle strip S which carry security prints. Suitable banding units for carrying out banding (also referred to as “banderoling”) are for instance disclosed in International application No. WO 20051085070 in the name of the present Applicant. In this example, the banding station BS comprises as many banding units as there are columns of security prints on each sheet, namely five (M=5) banding units in this example. The banding operation may be omitted or replaced by any other operation aimed at securing the securities together in the form of a bundle arrangement, such as by stapling.
Each bundle strip S of securities thus provided with securing bands, hereinafter referred to as a banded bundle strip S* of securities, is then fed out of the banding station BS to the subsequent processing station. In the illustrated example, each banded bundle strip S* of securities is fed laterally (along a direction opposite to direction x in FIG. 1) out of the banding station BS and then (along direction y) to a collating position where all banded bundle strips S* of securities of a given and same sheet stack SS are regrouped to form a stack-like formation SS* of N banded bundle strips S* of securities corresponding to the arrangement of the original sheet stack SS. In the stack-like formation SS*, the banded bundle strips S* are typically located close to one another or even abutting against each other.
The thus assembled stack-like formation SS* of banded bundle strips S* of securities is then fed stepwise (along direction x) through a second cutting station CS2 where the stack-like formation SS* is cut along the columns of security prints so as to output successive sets 2 of bundles 5 of securities, all banded bundle strips S* being cut simultaneously and stepwise by the second cutting station CS2. In this example, five (M=5) successive sets 2 of bundles 5 of securities, each provided with a securing band, are produced as a result of the column-wise cutting of each stack-like formation SS*, each successive set 2 consisting of a given number of bundles 5 of securities disposed next to the other, namely ten (N=10) bundles 5 of hundred individual securities each (i.e. the equivalent of one column of security prints of the original sheet stack SS). In the process, margins (not illustrated) at the right and left edges of the sheets (i.e. margins at the top and bottom of stack-like formation SS* in FIG. 1) are typically cut and discarded as well. Alternatively, as disclosed in U.S. Pat. No. 4,283,902, the right and left margins might be cut prior to feeding of the sheet stack SS to the first cutting station CS1 using additional cutting devices.
Each set 2 of bundles 5 of securities then needs to be evacuated before the next set 2 of bundles 5 arrives. Each bundle 5 of the set 2 must further be separated so as to form a flow a spaced-apart bundles 5, as schematically illustrated in FIG. 1. Such separation is necessary so that each bundle can be further processed individually, especially to form suitable stacks 75 of bundles 2 (referred to hereinafter as “bundle stacks”). This additional processing of the individual bundles 5 into bundle stacks 75 in particular includes the rotation by 180 degrees of every two bundle 5 (which alternate rotation of bundles is schematically illustrated in FIG. 1) so as to compensate for the typical thickness variations of the securities due, for instance, to the varying reliefs created as a result of intaglio printing, the presence of security elements applied onto selected regions of the substrate (such as OVD's—Optically Variable Devices) or of security element embedded locally in the substrate (such as watermarks, security threads, windows, etc.). In that respect, the securing band provided around each bundle is also typically applied at banding station BS in an offset manner with respect to the middle portion of each bundle.
Considering a typical processing speed of 10,000 sheets per hour, a new stack SS of hundred sheets will be supplied upstream of the first cutting station CS1 every thirty-six seconds (=(100*3,600)/10,000), which amounts to a new set 2 of N bundles 5, downstream of the second cutting station CS2, every 36/M seconds (or a new bundle 5 every 36/(M*N) seconds). In this example where each sheet carries five (M=5) columns and ten (N=10) rows of security prints, this means that a new set 2 of N bundles arrives every 7.2 (=36/5) seconds, i.e. a new bundle 5 every 0.72 (=36/(5*10)) seconds. The amount of time available to evacuate each set 2 of N bundles and carry out the above-mentioned bundle separation operation is thus limited.
Up to now, the bundle separation operation was carried out by separately seizing and accelerating each bundle of a set using adequate seizing and/or pushing members to create a sufficiently large spacing therebetween. This solution is however not satisfactory because it requires a relatively complex and large system for carrying out the separation of the bundles. There exists furthermore a substantial risk that a bundle is not properly seized or pushed by the seizing/pusher members, leading to jamming problems and, even worse, to irreversible damage to the bundles.
There is therefore a need for an improved solution which is of simpler and more robust configuration, while guaranteeing as much as possible a smooth processing of the bundles and reduce the likelihood of jamming and/or damages to bundles.
Furthermore, considering that the above-discussed processing of sheets stacks into individual bundles constitutes the final stage in the production process, close attention must be paid to both optical and physical quality requirements. Accordingly, it may be necessary to carry out a statistical process control during production, i.e. to remove one or more sample bundles out of the flow of bundles outputted downstream of the last cutting station in order to check the securities contained therein for errors or physical damage, especially in order to control that the securities have been cut properly and that the so-called print-to-cut register (i.e. the position of the imprints with respect to the cut edges) of the securities is correct. One cannot however merely take one or more bundles out of the flow of bundles, since this leads to a break in the sequence of bundles. A corresponding number of replacement bundles must either be inserted at the relevant places in the flow of bundles where sample bundles are taken or the sample bundles must be re-integrated in the flow after examination. Such operations shall be carried out during the finishing process without interfering with the continuous processing of the bundles. The reintroduction of sample bundle(s) in the production flow is particularly critical to carry out when producing an uninterrupted flow of bundles having a consecutive numbering sequence (as taught in International application No. WO 2004/016433 mentioned hereabove) as the sample bundle(s) may only be re-integrated at the correct position(s) in the production flow.
With the known solutions, a statistical process control is very difficult to implement due to the mechanical configuration of the system and to time constraints (there is typically not sufficient time to take one or more sample bundle(s) out of the flow and insert replacement bundle(s) or reintroduce the sample bundle(s) after examination).
There is accordingly a need for an improved process and system for processing bundles of securities.